Montgomery, Douglas C.; Peck, Elizabeth A.; Vining, G. Geoffrey (2012). Introduction to Linear Regression Analysis (5th ed.). Wiley. p. 218. ISBN978-0-470-54281-1. Retrieved 22 February 2013. Thus, DFFITSi is the value of R-student multiplied by the leverage of the ith observation [hii/(1 − hii)]1/2.